Tuning the Hardness and Wettability of Methacrylate Polymers

Abstract

<p>Silicones exhibit a fundamentally hydrophobic character. While the incorporation of hydrophilic surface moieties can be achieved by a variety of means, normally surface reversion leads to rapid recovery of hydrophobic surfaces. We were interested to learn if the hydrophobic character of silicones could be manifested on organic polymers and, moreover, if different degrees of wetting of organic surfaces could controlled by simultaneous use of more than one hydrophilic entity.</p> <p>Herein, we present a method to control the hardness and wettability of methacrylate polymers with the addition of ACR A008-UP, a polymerizable, acrylate-based trisiloxane surfactant. Surface wettabilities were determined through the use of contact angle measurements, and the hardness modulus is determined through the use of a Shore OO durometer. The wettability and the hardness of the polymers were controlled by varying the ratio of surfactant to methacrylate monomers. As the proportion of surfactant monomer increased, the hardness of the copolymers was depressed. In a similar fashion, as the proportion of surfactant increased, the copolymer surfaces became increasingly wettable. However, at a certain threshold concentration the wettability decreased once again, which is ascribed to the formation of a hydrophobic brush at higher concentrations. The wettability and hardness of the polymers, and the stability of the trisiloxanes on the surface will be discussed.</p>